Diagnosis

In many cases, doctors can diagnose sun allergy simply by looking at the skin. But if the diagnosis isn't clear-cut, you may need tests to help identify what's going on. These tests may include:

Ultraviolet (UV) light testing. Also called phototesting, this exam is used to see how your skin reacts to different wavelengths of ultraviolet light from a special type of lamp. Determining which particular kind of UV light causes a reaction can help pinpoint which sun allergy you have.

Photopatch testing. This test shows whether your sun allergy is caused by a sensitizing substance applied to your skin before you go into the sun. In the test, identical patches of common sun allergy triggers are applied directly to your skin, typically on your back. A day later, one of the areas receives a measured dose of ultraviolet rays from a sun lamp. If a reaction occurs only on the light-exposed area, it likely is linked to the substance being tested.

Blood tests and skin samples. These tests usually aren't needed. However, your doctor may order one of these tests if he or she suspects your symptoms might be caused by an underlying condition, such as lupus, instead of a sun allergy. With these tests, a blood sample or a skin sample (biopsy) is taken for further examination in a laboratory.

Treatment

Treatment depends on the type of sun allergy you have. For mild cases, simply avoiding the sun for a few days may be enough to resolve the signs and symptoms.

Medications

Creams containing corticosteroids are available over-the-counter and in stronger prescription forms. For a severe allergic skin reaction, your doctor may prescribe a short course of corticosteroid pills, such as prednisone.

The malaria medication hydroxychloroquine (Plaquenil) may ease the symptoms of some types of sun allergies.

Therapy

If you have a severe sun allergy, your doctor might suggest gradually getting your skin used to sunlight each spring. In phototherapy, a special lamp is used to shine ultraviolet light on areas of your body that are often exposed to the sun. It's generally done a few times a week over several weeks.

Lifestyle and home remedies

These steps may help relieve sun allergy symptoms:

Avoid sun exposure. Most sun allergy symptoms improve in less than a day or two if you keep the affected skin out of the sun.

Stop using medications that make you sensitive to light. If you're taking medications for other conditions, talk with your doctor about whether you can stop taking them if they are making your skin more sensitive to the sun.

Preparing for your appointment

You're likely to start by seeing your family doctor or primary care provider. Or when you call to set up an appointment, you may be referred to a doctor who specializes in skin conditions (dermatologist).

At the time you make the appointment, be sure to ask if you need to do anything in advance. For example, if you're going to have tests that check for a reaction to ultraviolet light (phototesting), your doctor may ask you to stop taking certain medications beforehand.

What you can do

Before your appointment, you may want to list answers to the following questions:

How long after exposure to the sun did your symptoms begin?

What type of symptoms did you experience?

Have your symptoms worsened or gotten better?

Have you ever had these types of symptoms before?

What medications and supplements do you take regularly?

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Examples may include:

What parts of your body are affected?

Exactly what does the affected skin look like?

How severe are your symptoms?

How long does your skin reaction last?

Do you have itching or pain?

Does your skin react just to direct sunlight or also to sunlight shining through window glass?

Does anyone else in your family have skin reactions to sunlight or other allergic skin conditions?

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